The causes of childhood leukemia remain largely unknown. The purpose of this proposal is to expand an existing case-control study of molecular of childhood leukemia in size and geographic region and refine the measurement of exposure to household chemicals and pesticides, and to assess exposure to electric and magnetic fields. The temporal relationship of exposure to environmental agents including dietary, occupational and residential chemical exposures are determined by use of self-report and interview data. Molecular biologic techniques are used to characterize the subtypes of leukemia and the presence of genetic changes. Biological specimens include bone marrow and peripheral blood of newly diagnosed cases, buccal cell specimens from cases, their mothers and control subjects, and archived newborn blood from cases and controls born in California will be used in the endeavor to identify the timing of exposures. Household pesticides are an environmental exposure of particular concern since previous studies have suggested that chemical and pesticide exposure during pregnancy and after birth may be related to the subsequent development of childhood leukemia. This research will expand a currently funded study of childhood leukemia which includes newly diagnosed cases ages 0-14 which present at four Bay Area referral hospitals during the period 1995-1998. This proposal will double the expected sample size to 400 cases by including cases ascertained at these hospitals an additional three years and expanding the study to include patients from the three major clinical centers for the central valleys of California for four years. Two matched control groups will be obtained for each case: friend controls and birth certificate controls. Friend controls will be randomly chosen from nominees provided by parents that match the case on age, sex, gender, county of residence at diagnosis, and ethnicity of mother. Birth certificate controls will be chosen from California births that match the case with respect to age, sex, gender, county of residence at birth, and ethnicity. A self-administered questionnaire and personal interview will be obtained to collect data related to a spectrum of environmental exposures and other risk factors including dietary history and residential history and history of chemical exposures of the mother prior to and during pregnancy and the child, occupational history and reproductive history of the mother, and health history of the child. A subsequent exposure component will focus on exposures to household pesticides during the past year and during pregnancy and the first two years of the child's life and measure electric and, magnetic fields directly in the home and indirectly by trained staff coding residential wiring configurations. Molecular characterization of leukemia cases allows for the subclassification of leukemias on a biological basis, and will facilitate the linkage of exposures with leukemia subtypes in the analysis. The proposed study, which will attempt to link specific chemical components with genetic changes found in childhood leukemia, will help to reduce the percentage of leukemias for which there is no known cause.